On 11/07/2023 16:27, Liam R. Howlett wrote: > * Ryan Roberts <ryan.roberts@xxxxxxx> [230711 10:09]: >> On 20/01/2023 16:26, Liam R. Howlett wrote: >>> From: "Liam R. Howlett" <Liam.Howlett@xxxxxxxxxx> >>> >>> Use the vma iterator so that the iterator can be invalidated or updated >>> to avoid each caller doing so. >> >> Hi, > > > Hello! > >> >> I've bisected 2 mm selftest regressions back to this patch, so hoping someone can help debug and fix? The failures are reproducible on x86_64 and arm64. > > Thanks! That is a big help. Where did you start your bisection? I > assume 6.4? Yes, I'm working to get all the mm selftests running (and ideally passing!) on arm64. I working on v6.4 and it was broken there. I went arbitrarily back to v5.10 and it was working there, so bisected between them. > >> >> >> mlock-random-test: >> >> $ ./run_kselftest.sh -t mm:mlock-random-test >> TAP version 13 >> 1..1 >> # selftests: mm: mlock-random-test >> mlock() failure at |0xaaaaaaab52d0(131072)| mlock:|0xaaaaaaacc65d(26551)| >> not ok 1 selftests: mm: mlock-random-test # exit=255 >> >> This mallocs a buffer then loops 100 times, trying to mlock random parts of it. After this patch, the test fails after a variable number of iterations; mlock() returns ENOMEM. If I explicitly munlock at the end of each loop, it works. >> >> >> mlock2-tests: >> >> $ ./run_kselftest.sh -t mm:mlock2-tests >> TAP version 13 >> 1..1 >> # selftests: mm: mlock2-tests >> munlock(): Cannot allocate memory >> munlock(): Cannot allocate memory >> not ok 1 selftests: mm: mlock2-tests # exit=2 >> >> Here, a 3 page buffer is mlock2()ed, then the middle page is munlocked. Finally the whole 3 page range is munlocked, and after this patch it fails with ENOMEM. If I modify the test to split the final munlock into 2, one for the first page and one for the last, the test passes. >> >> >> Immediately prior to this patch (2286a6914c77 "mm: change mprotect_fixup to vma iterator"), both tests pass. >> >> From a quick scan of the man page, I don't think it explicitly says that its ok to call mlock/munlock on already locked/unlocked pages, but it's certainly a change of behavior and the tests notice, so I'm guessing this wasn't intentional? >> >> I'm not familiar with this code so it's not obvious to me exactly what the problem is, but I'm hoping someone can help debug? > > I think I see the issue and I'm working on a fix. I appreciate the > analysis and report, it really helps narrow things down. You're welcome! > > Regards, > Liam
